This deserves a mention in any class having to do with optical illusions!
I will bet that the loud voice vibrates the head; the eyes, being attached, also vibrate; you then perceive a vibration "on the screen" that is not on the screen, but in your receiving apparatus.
This is similar to the effect you get when you spread your fingers and wave your hand back and forth in front of a TV or monitor. Suddenly you have ten to fifteen fingers! Or when you look quickly from side to side at a projection screen showing an image made through a color wheel...the colors get messed up.
Now if you yelled real loud while waving your hand back and forth rapidly through the light beam coming from a projector with a color wheel..........
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
